1. What is the size of your plasmid?
2. What is the percent of your gel run?
3. Did you include DNA ladder if yes is the separation good?
4. Picture please.
5. What extraction method did you use?
6. Do you re-use your buffer / gel if yes too many times?
7. Is this the first run or twice with identical result?
8. Have your labmate having problem with their electrophoresis too?